Method and apparatus for inspecting pneumatic tire during production

ABSTRACT

An inspection method for inspecting beads provided on a tire building drum in process of production a pneumatic tire includes measuring a displacement amount in a radial direction on each of the beads lying axially on both sides of the drum with a distance sensor such as an eddy current sensor while rotating the drum, synthesizing displacement amounts so obtained on the beads on both the sides, calculating a harmonic of the displacement amounts in the radial direction of the beads by performing harmonic analysis on a resultant synthesized displacement amount, and determining whether the magnitude of the harmonic so calculated falls within a predetermined range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of copending U.S.application Ser. No. 11/494,668, filed Jul. 27, 2006, and further claimspriority from Japanese Patent Application No. 2005-219605, filed on Jul.28, 2005. The entire contents of these applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for inspecting apneumatic tire with respect to the eccentricity of beads thereof duringproduction. The invention also relates to a method for producing apneumatic tire by making use of the inspection method.

2. Description of the Related Art

Low uniformity of pneumatic tires causes vibrations in a vehicle. Due tothis, force variations occurring when they rotate are measured onpneumatic tires after production, and tires showing large forcevariations are disposed as defectives.

The variability of constituent members of tires being produced thatoccurs in steps of the tire production process is considered toconstitute one of the causes which deteriorate the uniformity ofcompleted tires. As one example of the variability, there is raised adeviation in center between bead wires and a tire body which occursduring bead setting, and in case a deviation like this occurs, theuniformity of a completed tire is largely affected.

Conventionally, however, there has existed no process control systemwhich controls the production process from the viewpoint of theuniformity, and hence, it is not until the uniformity of a completedtire is measured that a defect associated with low uniformity is found.Investigations for suspected causes of the defect are then carried outin the individual production steps to find eventually that themechanical accuracy associated with the bead setting caused the defect.This cause locating process is the case that often happens with thedeteriorated uniformity-related defect.

Due to this way of dealing with the defect, there have been causedproblems that all tires that had passed through the relevant beadsetting step until the defect was found are now defective, making lotsof defectives to be discarded and that the production, which had beenstopped when the defect was found, cannot not be resumed until the causeis verified.

Incidentally, the Japanese Unexamined Patent Publication (Kokai) No.2004-354258 describes a method for inspecting joint portions on a beltply made by joining circumferentially short strip-like sheet memberstogether where end portions thereof are joined to each other by wrappingthe belt ply around a tire building drum and measuring a radial run-outof the belt ply in the circumferential direction with a one-dimensionlaser sensor while rotating the tire building drum in that state. Inaddition, the Japanese Unexamined Patent Publication (Kokai) No.2004-354259 discloses a method for inspecting a tread rubber formed on atire building drum with respect to a contour configuration using a lasersensor. While these Japanese Unexamined Patent Publications are such asto disclose the inspection methods for inspecting pneumatic tires underproduction, the inventions disclosed therein are not such as to be madeto inspect on the eccentric amount of the beads.

Additionally, the Japanese Unexamined Patent Publication (Kokai) No.2004-101433 discloses a method for measuring a radial run-out (RRO) of abreaker with high accuracy and good efficiency using an eddy currentdisplacement sensor, but the method is intended to inspect completedtires as products and is not intended to measure the eccentric amount ofthe beads, either.

SUMMARY OF THE INVENTION

The invention was made in the light of the views pointed out above andan object thereof is to provide a method and apparatus which can reducelargely the amount of defects that are generated in association with lowuniformity and can also reduce time until the production is resumed bymeasuring and controlling the eccentric amount of beads after they havebeen set in place.

The inspection method according to the invention is a method forinspecting beads provided on a tire building drum in process ofproduction a pneumatic tire in which a displacement amount in a radialdirection is measured on each of the beads lying axially on both sidesof the drum with a non-contact distance sensor while rotating the drum.Then, displacement amounts so obtained on the beads on both the sides ofthe drum are synthesized, and a harmonic of the displacement amounts inthe radial direction of the beads is calculated by performing harmonicanalysis on a resultant synthesized displacement amount. When carryingout the calculation, normally, the displacement amounts obtained asdescribed above are averaged out over the beads on both the sides of thedrum, and a harmonic analysis is performed on a resultant averaged-outdisplacement amount. Then, whether or not the magnitude of the harmonicso calculated falls within a predetermined range is determined.

In addition, the inspection apparatus according to the invention is anapparatus for inspecting beads provided on a tire building drum inprocess of production a pneumatic tire which includes non-contactdistance sensors for detecting displacement amounts in a radialdirection of the beads lying axially on both sides of the drum, a dataobtaining unit for obtaining data related to the displacement amounts inthe radial direction of the beads for a single rotation of the drum fromthe distance sensors, a data processing unit for synthesizing thedisplacement amounts of the beads lying on both the sides of the drumusing the data obtained and calculating a harmonic of the displacementamounts in the radial direction of the beads by performing harmonicanalysis on a resultant synthesized displacement amount, and adetermination unit for determining whether or not the magnitude of theharmonic of the displacement amounts falls within a predetermined range.

In an embodiment of the invention, the distance sensors are made up ofeddy current sensors, and displacement amounts in a radial direction ofbead wires may be measured by measuring distances from the sensors tothe bead wires, respectively. Namely, while laser sensors can be used asthe distance sensors, in the event of laser sensors, when the bead wiresare covered with rubber such as a carcass ply or a rim strip, a distanceas far as the surface of the rubber is to be measured, and hence, it ishard to measure accurately an eccentric amount of the bead wire. Incontrast to this, in the event that eddy current sensors are used, evenin a case where the bead wires are covered with rubber, since distancesto the metallic bead wires can be measured, eccentric amounts of thebead wires which affect the uniformity of a tire to be produced can bemeasured accurately. In the event that the carcass ply contains metalliccords, however, since it is hard to measure the distance to the beadwire even with the eddy current sensor, the eddy current sensors becomeeffective in a case where the carcass ply is made of only non-conductivecords.

Thus, with the eddy current sensors used, in the event that the beadwires deviate in the axial direction of the drum, measured values becomedifferent from actual radial displacement amounts. Due to this, in theembodiment of the invention, deviation amounts of the bead wires in theaxial direction of the drum are measured using non-contact distancesensors, and the measured values by the eddy current sensors may becorrected based on the deviation amounts so measured so as to obtain thedisplacement amounts in the radial direction of the bead wires, wherebythe eccentric amounts of the bead wires can be measured with betteraccuracy.

In addition, the invention provides a pneumatic tire production methodcomprising forming a carcass ply on a tire building drum, setting beadson the carcass ply, measuring a displacement amount in a radialdirection of each of the beads lying axially on both sides of the drumwith a non-contact distance sensor while rotating the drum, synthesizingdisplacement amounts of the beads on both sides of the drum so obtained,calculating a harmonic of the displacement amounts in the radialdirection of the beads by performing harmonic analysis on a resultantsynthesized displacement amount, determining whether or not themagnitude of the harmonic so calculated falls within a predeterminedrange, preparing a green tire using the beads for which the magnitude ofthe harmonic is determined to fall within the predetermined range, andvulcanizing to mold the green tire.

According to the invention, since the beads are inspected on theeccentric amounts thereof, which affect largely the uniformity of acompleted tire, after they have been provided on the tire building drum,a defect can be detected in the midst of production. Due to this, thegeneration of defects is largely reduced in amount, thereby making itpossible to reduce material costs. In addition, a failed location in themechanical facility can be verified early, so as to enable the failureto be dealt with in a smooth fashion, thereby making it possible toreduce time during which the relevant mechanical part of the facility isout of operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary diagram which shows the configuration of aninspection apparatus according to an embodiment of the invention.

FIG. 2 is an enlarged sectional view of a main part of FIG. l.

FIG. 3 is a flowchart which shows the flow of a process according to theembodiment.

FIG. 4 is a sectional view of a pneumatic tire in a width direction of atread thereof.

FIG. 5 is a graph which shows a relationship between an output voltage(V) of a distance sensor and a detection distance α.

FIGS. 6A to 6D are graphs which show displacement amounts in a radialdirection of bead wires, in which FIG. 6A shows data on a serial side,FIG. 6B data on an opposite serial side, FIG. 6C an average waveformresulting from averaging out both the data, and FIG. 6D a waveform of afirst harmonic of the average waveform.

FIGS. 7A and 7B are graphs which show relationships between themagnitude of a first harmonic of a displacement amount of bead portionsin a tire as an intermediate product and the magnitude of a firstharmonic of RFV of the tire which is completed as a final product, inwhich FIG. 7A shows a relationship with correction and FIG. 7B arelationship without correction.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of the invention will be described byreference to the accompanying drawings.

FIG. 1 is an exemplary diagram which shows the configuration of aninspection apparatus 10 according to the embodiment. This inspectionapparatus 10 includes a pair of left and right, first and seconddistance sensors 12, 14 for detecting displacement amounts of beads 52,which are set on a tire building drum 50, in a radial direction thereof,a pair of left and right, third and fourth distance sensors 16, 18 fordetecting displacement amounts of the beads 52 in an axial direction ofthe drum, and a computer 20.

An inner liner 58 is wound around the tire building drum 50, and acarcass play 60 is then wound around the inner liner 58, whereafter thebeads 52 are set on both axial sides of the drum 50. Furthermore, thecarcass ply 60 is folded back (or turned up) axially inwards at bothedge portions in such a manner as to encompass therein the beads 52,respectively, whereby an intermediate product 70 is formed which is in amiddle step of a production process of a tire, and in this embodiment,this intermediate product is to be a target for inspection. The beads 52are each made up of a bead wire 54 which is made of a bundle of metallicwires formed into a ring shape and a rubber bead filler 56 which isdisposed on an radially outer circumference of the bead wire 54.

In addition, while there is imposed no limitation on the intermediateproduct which constitutes a target for inspection, provided that thebeads 52 have already been set on but no vulcanization has yet beencarried out on the intermediate product, in order to find a defect in asearly a step as possible, an intermediate product resulting immediatelyafter the carcass ply 60 has been turned up or one resulting immediatelyafter a rim strip 62 and/or a side wall 64 (refer to FIG. 4) have beenwound around the turned up carcass ply 60 are preferred as theintermediate product for inspection.

The tire building drum 50 includes a motor 80 functioning as arotational driving device, so as to be rotated by the motor 80. Inaddition, a rotational position sensor 82 such as an rotational pulseencoder is provided on the tire building drum 50 which functions as arotation detecting device for detecting a rotational position of thetire building drum 50. Angle information such as gears is providedcircumferentially on a rotational shaft 84 of the drum 50 at equalintervals, and data sampling, which will be described later on, ispreferably carried out at the intervals at which the angle informationis provided while detecting the angle information by the rotationalposition sensor 82. By carrying out the data sampling while obtainingposition information for each rotation of the rotational shaft 84 usingthe rotational position sensor 82, the intended sampling can be carriedout even though the drum 50 rotates irregularly, thereby making itpossible to obviate the necessity of waiting until the drum 50 comes torotate at constant speed.

The first and second distance sensors 12, 14 are non-contactdisplacement sensors and eddy current sensors are used in thisembodiment. The eddy current sensors are displacement sensors formeasuring distances between the sensors and measurement targets bygenerating eddy current in measurement targets (the metallic bead wires54) by alternate current magnetic fields from the sensors and detectingvoltages generated by the eddy current so generated. As shown in FIGS.1, 2, the distance sensors 12, 14 are provided at positions which lieclose to the axial end portions of the intermediate product 70 on aninner circumferential side thereof so as to radially face the bead wires54, respectively, to detect displacement amounts in a radial directionof the bead wires 54 by measuring distances a to the bead wires 54. Notethat the first distance sensor 12 is such as to measure a displacementamount of the bead wire 54 on a serial side of the intermediate product70 whereas the second distance sensor 14 is such as to measure adisplacement amount of the bead wire 54 on an opposite serial side.

The third and fourth distance sensors 16, 18 are non-contactdisplacement sensors. In the first and second distance sensors 12, 14,when the bead wires 54 deviate in the axial direction of the drum (forexample, a state indicated by chain double-dashed lines 54′ in FIG. 2) ,detected voltages become different. Then, in this embodiment, the thirdand fourth distance sensors 16, 18 are provided which can detectdeviation amounts of the bead wires 54 in the axial direction of thedrum (that is, in a lateral direction) , so that measured values by thefirst and second distance sensors 12, 14 are corrected based ondeviation amounts measured by the third and fourth sensors 16, 18. Asshown in FIGS. 1, 2, the sensors 16, 18 are provided at positions whichlie axially outwards of axial ends of the intermediate product 70 so asto axially face the bead wires 54, respectively, to detect deviationamounts of the bead wires 54 in the axial direction by measuringdistances β to the bead wires 54. While laser sensors can be used asthese sensors 16, 18, eddy current sensors are used in this embodiment.Note that the third distance sensor 16 is such as to measure a deviationamount of the bead wire 54 on the serial side whereas the fourthdistance sensor 18 is such as to measure a deviation amount of the beadwire 54 on the opposite serial side.

As the computer 20 that is connected to the first to fourth distancesensors 12, 14, 16 and 18, the motor 80 and the rotational positionsensor 82, for example, a normal personal computer or process controlmicroprocessor is used. A central processing unit (CPU) 22 of thecomputer 20 reads in a processing program from a memory 24 when thecomputer 20 is activated and functions as a data obtaining unit 26, adata processing unit 28 and a determination unit 30 and the like.

The data obtaining unit 26 receives displacement signals from the firstand second sensors 12, 14 (signals representing distances from thesensors to the bead wires 54) and obtains data on displacement amountsin the radial direction of the bead wires 54 for a single rotation ofthe drum. For example, the data obtaining unit 26 samples displacementsignals at a plurality of points which are arranged circumferentially atintervals of a predetermined angle (for example, 72 pointscircumferentially arranged at intervals of 5°) using the rotationalposition sensor 82 and obtains the displacement signals so sampled asdata for the single rotation of the drum.

In addition, the data obtaining unit 26 receives displacement signalsfrom the third and fourth distance sensors 16, 18 so as to also obtaindata on deviation amounts in the axial direction of the bead wires 54for the single rotation of the drum.

Furthermore, the data obtaining unit 26 corrects values measured by thefirst and second distance sensors 12, 14 based on the deviation amounts.To be specific, the data obtaining unit 26 determines whether or not thedeviation amounts fall within a predetermined range (for example, 1 mm),and since an axial deviation falling within the predetermined range canbe ignored, in case the deviation amounts fall within the predeterminedrange, the data obtaining unit 26 does not carry out the correction. Onthe contrary, in case the deviation amounts exceed the predeterminedrange, the data obtaining unit 26 corrects the values measured by thefirst and second sensors 12, 14 using a correction formula which isobtained in advance. As an example of this, relationships between theoutput voltage (V) of the first and second sensors 12, 14 and thedistance α are shown in FIG. 5 which result when there exists no axialdeviation and when there exists an axial deviation of 6 mm,respectively. A relationship like this is obtained in advance for eachdeviation amount, and corrections are carried out based on therelationships so obtained.

Thus, in the way that has been described heretofore, the data obtainingunit 26 obtains data on displacement amounts in the radial direction ofthe bead wires 54 for the single rotation of the drum on both the sides,the serial and opposite-serial sides, of the intermediate product 70,respectively.

The data processing unit 28 performs an averaging processing over theserial side bead 52 and the opposite serial side bead 52 using theradial displacement amounts of the bead wires 54 obtained by the dataobtaining unit 26 as described above. Namely, the data processing unit28 synthesizes waveforms of both the serial side and opposite serialside bead wires 54 so as to calculate an intermediate value. Thus, theinfluence due to the inclination of the intermediate product 70 relativeto the tire building drum 50 can be eliminated by composing to averageout the data of the beads 52 on both the sides of the intermediateproduct 70 like this. Since the overall inclination of the intermediateproduct 70 like this does not affect the radial run-out (RRO) and RFV(radial force variation) of a completed tire as a final product, onlythe eccentric amounts of the beads 52 which affect the uniformity of thetire can be obtained by averaging out the displacement amounts thereof.

In addition, the data processing unit 28 performs a harmonic analysissuch as Fourier analysis using the data on displacement amounts whichare averaged out as has been described above, that is, the data onfluctuation in the radial displacement amounts of the bead wires 54 inthe circumferential direction of the beads, so as to calculate, forexample, a first harmonic.

The determination unit 30 determines whether or not the magnitude of theharmonic of the displacement amounts that is calculated by the dataprocessing unit 28 as has been described above falls within apredetermined range (for example, 2.5 mm or smaller). Namely, arelationship between the harmonic and the uniformity (RFV, RRO) of acompleted tire as a final product is obtained in advance, and thedetermination unit 30 determines whether acceptable or unacceptablebased on the relationship.

The result of the determination is then displayed on a display unit 34.To be specific, in case the result of the determination is out of therange and hence is unacceptable, a monitor such as a display displaysthereon an indication in this respect or an alarm is raised by a warningdevice.

Next, an example of the flow of the inspection process will be describedfurther based on a flowchart shown in FIG. 3.

Firstly, in step a1, a signal is outputted to the motor 80 to rotate thetire building drum 50 on which the intermediate product 70 is provided.

Following this, in step a2, the data obtaining unit 26 obtains data onthe beads 52 lying on both the sides of the drum 50 for a singlerotation of the drum. Specifically speaking, the data obtaining unit 26samples displacement signals from the first and second distance sensors12, 14 every predetermined angle while detecting the angle informationpositions by the rotational position sensor 82 and then obtains thedisplacement signals so sampled as data for the single rotation of thedrum. As this occurs, while data only for the single rotation may beobtained, data are preferably measured for a plurality of rotations soas to be averaged out.

In addition, in step a3, the data obtaining unit 26 samples displacementsignals representing deviation amounts from the third and fourthdistance sensors 16, 18 every predetermined angle while detecting theangle information positions by the rotational position sensor 82 andthen obtains the displacement signals so sampled as data for the singlerotation of the drum. This step 3 a is normally performed at the sametime as step a2.

Then, in step a4, the data on the radial displacement amounts obtainedin step a2 are corrected based on the data on the deviation amountsobtained instep a3. To be specific, whether or not the data on thedeviation amounts obtained in step a3 fall within a predetermined rangethat has been inputted in advance via an input unit 32 is determined,and if the data do not fall within the predetermined range, the dataobtained in step a2 are corrected in accordance with the deviationamounts. On the contrary, if the data obtained in step a3 fall withinthe predetermined range, no correction is performed. Thus, the data onthe radial displacement amounts of the bead wires 54 for the singlerotation of the drum are obtained on both the sides, the serial andopposite-serial sides, of the intermediate product 70, respectively, inthe way that has been described heretofore, and the data so obtained arethen stored temporarily in the memory 24. Note that not only a keyboardbut also a various types of disk drives such as a floppy disk, CD andDVD are enumerated as the input unit 32.

Next, in step a5, the displacement amounts of the bead wires 54 areaveraged out over the serial side bead 52 and the opposite serial sidebead 52 by the data processing unit 28 using the data on thedisplacement amounts in the radial direction of the bead wires 54 storedin the memory 24. For example, FIG. 6A shows data on the displacementamount on the serial side, and FIG. 6B shows data on the displacementamount on the opposite serial side, and by averaging out both the data,an average waveform shown in FIG. 6C is obtained.

Next, in step a6, harmonic analysis is performed on the average waveformobtained in the previous step to calculate a harmonic of thedisplacement amounts in the radial direction of the bead wires 54. As anexample of this, a graph of a first harmonic obtained by performingharmonic analysis on the average waveform shown in FIG. 6C is shown inFIG. 6D.

Thereafter, in step a7, the determination unit 30 determines whether ornot the magnitude of the harmonic falls within the predetermined rangethat has been inputted in advance via the input unit 32, and if themagnitude is determined to fall within the predetermined range, theresult of the inspection is acceptable, and the inspection is completedthere. On the contrary, the magnitude of the harmonic exceeds thepredetermined range, the result is determined to be unacceptable, and anindication in this respect is displayed on the display unit 34.

Then, only intermediate products 70 that have passed the inspection areallowed to proceed to a subsequent tire building step, that is, belts 66and a tread 68 are wrapped around the intermediate product 70 that haspassed the inspection to thereby prepare a green tire, which is thenfinally vulcanized and molded so as to obtain a pneumatic tire as afinal product (refer to FIG. 4).

According to the embodiment that has been described heretofore, theeccentric amounts of the bead wires 54 after they have been set whichlargely affect the uniformity of a completed tire can be measured in themidst of production thereof. In particular, since the deviation amountsof the bead wires 54 in the axial direction of the drum are measuredusing the third and fourth distance sensors 16, 18 to thereby correctthe values measured by the first and second distance sensors 12, 14based on the deviation amounts, the eccentric amounts of the bead wires54 can be measured with good accuracy.

As an example of this, according to the embodiment, a first harmonic isobtained for the displacement amounts in the radial direction of beadwires 54 in an intermediate product of a radial tire of LT235/85R16 120Qafter the turning up of a carcass ply, and FIGS. 7A, 7B are graphs whichshow relationships between the magnitude of the first harmonic of theradial displacement amount of the bead wires 54 so obtained and themagnitude of a first harmonic of RFV of the tire completed as a finalproduct. Here, the air pressure of the tire when an RFV was measured was300 kPa, and a load imposed on the tire at the time of measuring the RFVwas 7551N. FIG. 7A shows a relationship resulting when the correctiondescribed as occurring in step a4 using the third and fourth distancesensors 16, 18 was carried out, whereas FIG. 7B shows a relationshipresulting when no such correction was carried out. As is clear from thegraphs, a correlation coefficient resulting when the correction wascarried out was R=0.925, which is higher than a correlation coefficient,R=0.883, which resulted when no correction was carried out, and it isunderstood from this that defects can be detected with better accuracyby carrying out the correction.

Thus, as has been described heretofore, according to the embodiment,since defects can be detected in process of production of tires, thedefects so detected can be dealt with in the early step, and the amountof defects to be generated can be reduced largely, thereby making itpossible to reduce costs for materials. In addition, a failed locationin the mechanical facility can be identified early, so as to enable thefailure to be dealt with in a smooth fashion, thereby making it possibleto reduce time during which the relevant mechanical part of the facilityis out of operation.

According to the invention, since the defect can be detected which istriggered by the eccentricity of the beads in the intermediate productin the midst of production and which affects largely the uniformity of atire completed as a final product, the invention can be used to controlthe process of production when producing various types of pneumatictires.

1.-15. (canceled)
 16. An apparatus for inspecting beads provided on atire building drum in a process of production of a pneumatic tire,comprising: non-contact distance sensors which detect displacementamounts in a radial direction of beads provided axially on both sides ofthe tire building drum; a data obtaining unit configured to obtain datarelated to the displacement amounts in the radial direction of the beadsfor a single rotation of the drum by the distance sensors; a dataprocessing unit configured to synthesize the displacement amounts of thebeads lying on both the sides of the drum using the data obtained andcalculate a harmonic of the displacement amounts in the radial directionof the beads by performing harmonic analysis on a resultant synthesizeddisplacement amount; a determination unit configured to determinewhether or not the magnitude of the harmonic so calculated of thedisplacement amounts falls within a predetermined range, each distancesensor being an eddy current sensor, and wherein each bead comprises abead wire and a displacement amount in the radial direction of a bead ismeasured by measuring a distance from a respective distance sensor tothe bead wire of a respective bead; and a non-contact distance sensorwhich detects a deviation amount of the bead wire in an axial directionof the drum, whereby a measured value measured by each non-contactdistance sensor that is an eddy current sensor is corrected based on thedeviation amount so measured to obtain the displacement amount in theradial direction of the bead wire.
 17. An inspection apparatus as setforth in claim 16, wherein the non-contact distance sensor whichmeasures the deviation amount is an eddy current sensor.
 18. Aninspection apparatus as set forth in claim 16, wherein the determinationunit determines whether or not the magnitude of the harmonic of thedisplacement amounts falls within a tolerance which is predeterminedbased on a relationship between the magnitude of the harmonic and theuniformity of a completed tire as a final product.